1. Field of the Invention
The invention relates to photopolymerizable compositions, especially for dental purposes, containing photopolymerizable olefin compounds, especially acrylic and/or methacrylic compounds, as well as at least one ketone and one amine as activating substances.
2. Discussion of Prior Art
Photopolymerizable compositions on the basis of olefin compounds, especially acrylic and/or methacrylic compounds are known, which contain .alpha.,.alpha.-diketones which absorb visible light in the wavelength range of 300 to 500 nm. Important representatives of these ketones are benzophenone, benzil and camphorquinone. One important field for the application of these photopolymerizable compositions is dentistry.
In the preparation of, for example, varnishes, paper coatings or dental fillings, the photopolymerizable compositions can be catalyzed only with these ketones and can be set by visible light. Relatively thin layers are set in this manner, and this takes a relatively long time. To shorten the setting time, it is known to add to the photopolymerizable compositions, in addition to the ketones, amines having CH groups in the alpha position. Examples of such amines are triethanolamine, dimethylaminoethanol and dimethylaminoethylmethacrylate.
These amines have a disagreeable odor; furthermore, their toxicity and their relatively weak accelerating or activating action are disadvantageous. In general, they produce approximately only a doubling of the rate of reaction.
Amines such as N,N-dimethylaniline, N,N-dimethyl-p-toluidine or N,N-dimethyl-sym.-xylidine, have a definitely better accelerating action in the photopolymerizable compositions. However, the addition of these substances often results in a severe brown discoloration of the polymer. Even in this case the accelerating action is not yet satisfactory.